Deoxidation of alkalinous halides



DEOXIDA'IION (BF ALKALINOUS HALIDES Frank X. McCawley, Cheverly, MtL, assignor to Chicago Development Corporation, Riverdale, Mil, a corporation of Delaware No Drawing. Application November s, 1957 Serial No. $4,092

2 Claims. (Cl. 204-64) This application is a continuation in part of my copending application, Serial No. 579,445, filed April 20, 1956, for Deoxidation of Alkalinous Halides.

This invention relates to the removal of oxygen from fused alltalinous halide baths. It has for its object the provision of oxygen free baths of such halides with the addition of metallic halides for electrolytic baths for electrodepositing titanium group metals and the like. It applies to baths containing alkalinous chlorides and bromides, and it is to these halides of the alkali metals, alkaline earth metals and magnesium that I refer by the term alkalinous halides.

It is well known that when crystalline alkalinous halides either alone or in combination are melted there is some hydrolysis and the resulting melt contains oxygen presumably as alkalinous oxide. Various procedures have been suggested for removing this oxygen or reducing it to a point where it is no longer objectionable. For use in titanium chloride electrolytes, deoxidation by means of more or less finely divided titanium has been proposed. The idea here has been that if the oxygen bath is allowed to react with titanium, and the solid product removed, the bath will no longer react with titanium. In practice, however, this procedure is unsatisfactory because the titanium added for deoxidation forms a surface coating of TiO which is in equilibrium with the bath as follows:

TiO-l-MCI ZTiCI l-MO (l) where M is a divalent alkalinous metal. The bath accordingly still contains oxygen. The coating of TiO on the titanium in this instance can be demonstrated by X-ray spectrometry. My invention consists in adding TiO to the bath in excess. This oxide is substantially insoluble in the halide bath, but reacts with the dissolved alkalinous oxide to form an insoluble titanate, which can likewise be identified by X-ray spectrometry. Since neither the TiO nor the insoluble titanate react with titanium, the bath does not oxidize titanium even when the solids are allowed to remain in the bath.

As a matter of fact, I have found that the presence of suspended TiO in a bath for the anodic solution of titanium is advantageous since it insures that oxygen in the anode will be dissolved according to the equation:

2,858,258 Patented Oct. 28, 1958 linous halide bath the formation of titanium is by reaction of the titanium halide with a solution of alkalinous metal formed at the cathode. The reducing power of these solutions is such as to reduce titanium halides, not necessarily titanium ion, to metal without reducing TiO The addition of TiO to electrolytic baths for refining titanium is therefore particularly useful for all such baths in which titanium metal is produced by reaction of the halide with alkalinous metal.

I have found that zirconium dioxide behaves in a manner identical with titanium dioxide and that chloride baths for electrorefining zirconium may be treated with Zr0 for removing soluble oxygen therefrom.

Having now described my invention, I will illustrate it by examples.

Example I In this example, I take a vessel having an inert atmos' phere and melt lbs. of sodium chloride and heat to 850'. C. I now add 1 lb. of pure dry finely divided Ti0 and mix into the melt. I filter this melt through sintered stainless steel and find by analyses that it contains less than 1 p. p. In. oxygen.

Example II I take the melt prepared above, but before treatment with TiO and add 1 lb. finely divided pure titanium containing 02% oxygen. When the metal has settled, I remove it and wash with water to remove salts. The titanium now contains .15 oxygen and X-ray analysis shows the surface of the titanium to be covered with TiO.

Example III I take the above treated salt and add 1 lb. of finely divided titanium containing 02% oxygen. The titanium is allowed to settle and removed as before. It is found to contain .08% oxygen.

Example IV I take the product in Example I without filtration and add 1 lb. of finely divided pure titanium containing .02% oxygen and recover the metal as in the preceeding examples. It was found to contain .02% oxygen.

Example V I take a melt containing NaCl and 5% Ti as TiCl and place it in an electrolytic cell provided with an inert atmosphere. tanium anode containing 3% iron, 0.5% oxygen, 0.2% chromium and cathode of steel. The geometry of the cell and the electrodes and the current density is so arranged that refining proceeds with an open circuit voltage of the cell slightly reverse to the applied Voltage. I operate this cell for the production of 100 grams of cathode product. This product analyzes 003% iron, .001% chromium, and 0.21% oxygen. I now add TiO in an amount of 1% of the electrolyte by weight and produce a further 100 grams of cathode product. This product analyzes 003% iron, .001% chromium, and .007% oxygen.

Example VI I proceed as in Example V, except that I use an electrolyte of 65% SrCl -35% NaCl. It is impossible to find conditions at which a cell with this electrolyte will operate with a reverse open circuit voltage so I operate with an open circuit voltage of 0.1 v. in the same di rection as the applied voltage. The first 100 grams produced show 003% iron, 1.2% chromium, .and .5% oxygen. I then add titanium dioxide which does not aifect the composition of the deposit. I now provide a battle to prevent convection, but not diffusion, from anode zone to cathode zone. I replace the electrolyte with the original bath and add 1% TiO around the The cell is provided with an impure ti- Example VII I proceed exactly as in Example 1, except that I add ZrO in place of TiO The result so far as deoxidation is concerned is identical with that of Example I.

Example VIII I proceed as in Example V, except that I use an electrolyte of 50% MgCI 50% NaCl and 2% Zr as chloride.

The cell is provided with an impure Zirconium anode containing 3% iron, and 1% oxygen. The cathode is steel. The cell is operated at a cathode current density of 200 amperes per square foot. The Zr formed is flaky and is only partly adherent to the cathode. When recovered from the melt, this zirconium analyzes .02% iron and .5% oxygen. I now add ZrO in an amount of 1% of the electrolyte and allow the bath to settle. I now continue electrolysis as before and obtain 100 grams of zirconium product analyzing .003% iron, oxygen, balance substantially zirconium.

What is claimed is:

1. In a process for the production of a metal selected from the group titanium and zirconium by electrolysis of a soluble anode containing a metal of the above group in a fused salt melt consisting of at least one halide of the group consisting of chlorides and bromides of alkali and alkaline earth metals and magnesium contaminated with a significant amount of a contaminant of the group consisting of alkali and alkaline earth metal oxides and magnesium oxide, the improvement which comprises rendering the melt substantially oxide free by the addition thereto of dry substantially pure finely divided dioxide of a metal of the first group above in an amount suflicient to react with all of the said oxide present to convert said oxide to an insoluble salt of the group consisting of titanates and zirconates of alkali and alkaline earth metals and magnesium While maintaining the reactants under an inert atmosphere.

2. The process of claim 1 in which the metal is titanium and the oxide added is TiO No references cited. 

1. IN A PROCESS FOR THE PRODUCTION OF A METAL SELECTED FROM THE GROUP TITANIUM AND ZIRCONIUM BY ELECTROLYSIS OF A SOLUBLE ANODE CONTAINING A METAL OF THE ABOVE GROUP IN A FUSED SALT MELT CONSISTING OF AT LEAST ONE HALIDE OF THE GROUP CONSISTING OF CHLORIDES AND BROMIDES OF ALKALI AND ALKALINE EARTH METALS AND MAGNESIUM CONTAMINATED WITH A SIGNIFICANT AMOUNT OF A CONTAMINANT OF THE GROUP CONSISTING OF ALKALI AND ALKALINE EARTH METAL OXIDES AND MAGNESIUM OXIDE, THE IMPROVEMENT WHICH COMPRISES RENDERING THE MELT SUBSTANTIALLY OXIDE FREE BY THE ADDITION THERETO OF DRY SUBSTANTIALLY PURE FINELY DIVIDED DIOXIDE OF A METAL OF THE FIRST GROUP ABOVE IN AN AMOUNT SUFFICIENT TO REACT WITH ALL OF THE SAID OXIDE PRESENT TO CONVERT SAID OXIDE TO AN INSOLUBLE SALT OF THE GROUP CONSISTING OF TITANATES AND ZIRCONATES OF ALKALI AND ALKALINE EARTH METALS AND MAGNESIUM WHILE MAINTAINING THE REACTANTS UNDER AN INERT ATMOSPHERE. 